Apparatus for superfinishing of rotary crankpins of crankshafts

ABSTRACT

Apparatus includes both at least one superfinishing tool and a grinding device which are designed to simultaneously machine crankpins of crankshafts. The grinding device which is controlled by a leveling arrangement functions to assure that the crankpin is parallel with the axis of the center pin of the crankshaft.

United States Patent 91 Runge 51 Jan. 16, 1973 $41 APPARATUS FOR SUPERFINISHING or ROTARY CRANKPINS 0F CRANKSHAFTS [76] Inventor: lleinert Runge, Borchshoher Str. 129, Bremen-Schonebeck, Germany 22 Filed: Dec.22, 1970 21 Appl.No.: 100,584

[30] Foreign Application Priority Data Dec. 6, 1969 Gennany ..P 19 61 279.4

[52] US. Cl. ..Sl/3, 51/55, 51/73 GC [51] Int. Cl. .3241) 5/42 [58] Field of Search.5l/3, 55, 56, 90,105 SP, 241 B, 51/73 [56] References Cited UNITED STATES PA'IENTS 1,774,337 8/1930 Sickel .51/56 2,639,559 5/1953 Price ..51/1()5 SP 3,456,391 7/1969 Venesia... .l...51/24l B 2,698,505 l/1955 Marsh ..5l/43 X 2,597,167 5/1952 Musyl ..51/90 X Primary Examiner-Harold D. Whitehead Att0mey-Lowry, Rinehart, Markva & Smith [5 7 ABSTRACT Apparatus includes both at least one super-finishing tool and a grinding device which are designed to simultaneously machine crankpins of crankshafts. The grinding device which is controlled by a leveling arrangement functions to assure that the crankpin is parallel with the axis of the center pin of the crankshaft.

8 Claims, 4 Drawing Figures PATENTEUJAH 16 I975 SHEET 2 UF 3 FIG. 2

IN VEN TOR HEM Em" IPWVGE APPARATUS FOR SUPERFINISHING OF ROTARY CRANKPINS OF CRANKSHAFTS The invention relates to apparatus for finishing rotary crankpins of crankshafts wherein the apparatus comprises least one superfinishing tool and a grinding roller both mounted on the same carrier which is arranged on a mounting support such that it will follow the rotary movement of the crankpin about the trunnion of the crankshaft.

Apparatus for superfinishing crankpins of crankshafts by means of a superfinishing tool located on a movable mounting support is known in the art. Movement is provided by a parallel construction formed by two parallelogram linkages arranged in series on which a tool carrier supporting the superfinishing tool is arranged. The tool carrier has rollers for supporting it on the crankpin to be finished. Frequently, two superfinishing tools are provided on the same carrier which act upon the crankpin to be machined simultaneously at a relatively large angular spacing from one another about the crankpin.

ln machining of crankpins of large-size crankshafts with a pin diameter exceeding about 400 mm., it is particularly difficult to achieve axial parallelism of the surface of the crankpin with respect to the center bearing pin. The inaccuracy is attributed to the fact that with such large crankshafts the crankpin processing machines comprise a rotary lathe tool which operates while the crankshaft is stationary. ln this case inaccuracies arise for several reasons, namely on the one hand through the necessary bearing play of the turn-table ring on which the tool is mounted and on the other hand by the misalignment of the swivel head with the axis of the crankshaft. These defects lead to the axis of the crankpin extending parallel to the axis of the center bearing pin only on rare occasions. If the crankpin is not parallel with the center pin it leads to a nonuniform bearing play and to poor contact between the bearing parts and the danger exists that the piston in the cylinder barrel, which is at right angles to the base plate and to the bearing bore of the center bearing, will be tarnished at one side. Thus increased and premature wear may be brought about.

The correction, to bring about parallelism of the axis of the crankpin with the axis of the center bearing pin, that is the so-called liquid level correction, is accomplished in general by hand machining. This is not only very complicated, tiresome and expensive, but experience has shown that hand machining rarely satisfactorily improves the contact between the bearing parts. The work must be carried out by specialists who are rarely available nowadays. Moreover, in this instance everything depends on the dexterity of the person carrying out the machining. In many cases one falls below the nominal diameter of the crankshaft during hand machining before attaining the axial parallelism thus making the exchange of bearings only rarely possible. Moreover, machining is restricted to the adjustment of the bearing pertaining to a particular crankpin. This means that the bearings for the crankpins cannot be exchanged between one another.

The object of the invention is to achieve the liquid level correction at the same time as the superfinishing of the rotating crankpin, mechanically. In a superfinishing apparatus for the rotating crankpin of crankshafts, in which the carrier is suspended on a mounting support and is movable in a planar sense as well as being supported by means of rollers on the crankpin, the invention is distinguished by the fact that a grinding device for the crankpin is associated with the superfinishing tool, the grinding device being controllable in response to a liquid level control whereby it is maintained parallel to the axis of the center bearing pin of the crankshaft. Preferably, an electronic liquid level control is used.

In this way a liquid level correction for the rotating crankpin can be effected at the same time as the machining of the rotating crankpin of the crankshaft guaranteeing maximum accuracy. A perfect contact for the bearing surface is obtained. The crankpin is steadily conveyed during the superfinishing with the superfinishing tools axially parallel with. the center pin of the crankshaft or is so held while the crankshaft rotates as in operation. This machining process with rotating crankshafts mounted in the operational condition is in no way similar to the machining process with the crankshaft stationary and thus leads to particularly high machining accuracy. Minimum possible tolerances result when crankpins are machined according to the invention, so that the crankshaft and the bearings undergo the minimum possible stress. This again guarantees perfect running and long working service of the crankshaft and thus of the diesel engine. Engines with crankpins machined according to the invention are capable of operating for longer period of time without bearing damage and crankshaft wear. Furthermore, it is possible to exchange bearings on the crankshaftsince the crankpins are all uniform, something which could not be achieved heretofore with hand machining. Commercial economy is ensured as a result. The bearing no longer needs to be specially matched to each crankpin and replacement bearings can be used from stock. Repairs may also be carried out even with crankshafts remaining in the engines, dismounting of the crankshaft and reconditioning in the workshop are not required. Thus the repair time and the turn-round time in the case of a ship are substantially reduced. The additional grinding device for the crankpin is preferably in the form of a driven grinding roll and can be swung about an axisof rotation extending transverse to the roll axis whereby the swingability can be regulated by a liquid level control. Preferably the liquid level is in the vertical plane passing through the axis of the grinding roll above the transversely extending swivel axis, which improves the accuracy.

To adjust the grinding roll a rod may be connected with the swivel frame carrying the grinding roll, and this rod can be moved by means ofa spindle driven by a stepping motor. There is thus the possibility of an extremely large fine adjustment.-

According to a further feature of the invention, the grinding tool, liquid level and swivel device may form a structural unit which can be adjusted in the height direction to the tool carrier with the superfinishing tools. In this way the structural unit can be moved forward to the crankpin by means of a stepping motor and roller tables. Moreover, the structural unit may be arranged on the tool carrier between the conveying sliding carriages carrying the superfinishing tools and displaceable longitudinally of the crank pins. It does not therefore take up any additional room outside of the tool carrier so that the apparatus according to the invention can be used both in the workshop and with crankshafts while in engines outside the workshop.

To improve the concentricity on machining the crankpin the arrangement of the guide rollers relative to the grinding stones of the superfinishing tools is of considerable importance. The center of the crankpin considered in cross-section should be outside a straight line extending between the location at which the guide rolls and the cutting position of the superfinishing tools contact the crankpin. The cutting position of the superfinishing tool preferably extends in a radial plane whose angle of inclination to the horizontal passing through the center of the crankpin is between about 35 to 10. With such an arrangement the concentricity of the crankpin can be improved.

The invention will now be explained with reference to an embodiment as shown in the drawings:

H6. 1 is an elevational view of the apparatus generally for superfinishing rotary crankpins of crankshafts including the apparatus according to the invention for the liquid level correction;

FlG. 2 is a more detailed elevational view of the tool carrier per se with the built-in structural unit for the liquid level correction; and

FIGS. 3 and 4 are cross-sectional elevations taken along the lines Ill-Ill and lV-IV, respectively, of the tool carrier of FIG. 2.

The illustrated apparatus 1 for superfmishing the crankpin 2 of the crankshaft 3 is provided with a mounting support 4 which is suitable for uniformly following the circular motion of the crankpin 2 about the center pin 3 of the crankshaft. Transmission lines, such as compressed air, electric current, lubricant and cooling medium, ect. extend along the mounting support to supply the finishing apparatus. A parallel construction is provided on a stationary support, this parallel construction being constituted by the two consecutive parallelogram linkages 6 and 7. The parallelogram linkage 6 is pivotally mounted at 8 and 9 on a rotary support and at 10 and 11 on an intermediate plate 12, while the parallelogram linkage 7 is pivotally mounted at 13 and 14 on the intermediate plate 12 and at 15 and 16 on the tool carrier 17.

The tool carrier 17 is composed of side plates 18 and 19 which are securely fixed together in a spaced parallel relationship by means of bolts 20. Spindles 27 and 28 extend between the side plates 18 and 19 and parallel to the axis of the crankpin 2, and conveying devices 25 and 26 include sliding carriages for movement along the spindles. The two superfinishing tools 21 and 22 are mounted on the ends of intermediate members 23 and 24 respectively which are supported on the conveying devices 25 and 26. The tool carrier 17 is supported on the crankpin 2 to be machined by means of the two guide rollers 29 and 30 rotatably between the side plates 18 and 19.

To carry out the liquid level correction, that is to insure the axis of the crankpin is parallel with the axis of the center pin of the crankshaft, there is an additional grinding device 31 which is a driven grinding roll 32. The grinding roll 32 is rotatably mounted in the stirrupshaped mounting 34 which inincludes a transversely extending plate 35. The parts 34 and 35 with mounting arms 350 form a rigid unit with the grinding roll 32, the

unit being mounted to swing about the axis 36 which is perpendicular to the rotational axis of the grinding roll 32. A liquid level device 37 is mounted on the plate 35 centrally above the grinding roll 32, an electronic control (not shown) being actuated by the level 37. Liquid level devices for controlling machine tools are well known in the art and are not per se a part of the present invention. One such known liquid level device suitable for use in the present invention is described in detail in US. Pat. No. 1,774,337 issued Aug. 26, 1930 to Sichel. The plate 35 with the mounting arms 35a is rotatably mounted by means of tapered roller bearings 38 between parallel plates 40 which are fixed to grinding carrier plate 39. The housing 41 cover the roller bearings 38. A rod 42 is fixedly secured to the transverse plate 35 and at the upper end of the rod there is a link rod knob 42a which co-operates by means of a tapered link 43 with a threaded spindle 44. Drive of the threaded spindle 44 is effected by a stepping motor 45 which rotates the shaft 48 via pinions 46 and 47, and thus the spindle 44. In this way the grinding roll 32 and the axis 36 can be adjusted depending on the position of the level 37 which locates a plane parallel to the axis of the center pin of the crankshaft. The angular position of the grinding roll 32 is held and secured by the stepping motor 45.

The grinding roller 32, the liquid level 37, the swinging mechanism 42 to 48 together with the grinder carrying plate 39, and the intermediate plate 40, make up a central unit which is within the tool carrier 17, that is, between the side plates 18 and 19. This structural unit may be adjusted within the tool carrier 17 in the height direction by means of an elevating mechanism 49. A nut 50 is secured to the side plate 18 by means of the holder 51. A threaded spindle 52 rotates in the nut, the spindle being driven via the pinion 53 and 54 by means of a stepping motor 55. The mounting support 56 for the stepping motor is fixedly mounted on the grinder carrier plate 39. The grinding roller 32 may be moved into contact with the surface of the crankpin 2 to be machined by means of the stepping motor 55. The height-adjustable unit is guided on the vertical guides 61 and 62 which may include rollers.

To align the emery cover on the grinding roller 32 there is an aligning device 57. Diametrically disposed callipers 58 are provided in the horizontal central plane of the crankpin 2 for the adjustment of the superfinishing tools 21 and 22 and the grinding roller 32, the callipers being connected with an electronic measuring device. The control boards 59 and 60 of the apparatus are preferably mounted on a console, for example, on the lower support of a turning lathe.

For operation of the tool according to the invention, the crankshaft is zeroed with the central bearing pin in the liquid level position on, for example, a center lathe. Each central pin receives a backrest hearing so that in practice there is a workable crankshaft bearing for the machining. The tool carrier 17 is set-up on the crankpin 2 to be machined, by means of the guide rolls 29, 30. The crankshaft is then rotated at, for example, 2 revolutions per minute. it is possible through the parallel linkage construction 4 to guide the tool carrier 17 at a uniform speed between the crankpin 2 and the grinding roller 32 or superfinishing tools 21, 22. Any nonuniform movement through another stationary bearing will only impair the concentricity of the pin by irregular abrasion. The grinding roller 32 is brought up to the crankpin 2 to be machined, by means of the stepping motor 55 via the threaded spindle 52 and the nut 50. The liquid level device 37 makes it possible for the grinding roller 32 to be maintained constantly zeroed in the liquid position when the crankshaft is rotating. The further stepping motor 45 actuates by means of the transmission 46, 47 the threaded spindle 44, by means of which and the connecting rod 42 the grinding roller 32 is brought by way of the pivot bearing 38 into the desired zeroed position. The grinding roller 32 is driven by means of a built-in three-phase current motor of the external rotor type. The liquid level aligment of the crankpin 2 is obtained through the grinder process by means of the grinding roller 32. The surface finish of the crankpin is improved up to about two-thousandths and the carrying attachment of the crankpin to above 90 percent by means of the superfinishing tools 21 and 22. The slope of the crankpin, which may be in the region of about 0.24 mm/m. to 0.08 mm/m., is removed by means of the grinding roller 32.

The apparatus may be used to repair crankshafts even when the crankshafts remain in the engine block. In this case, the crankshaft with a rotary device provided on the engine is rotated at about one-third of a revolution per minute. The zero level position is adjusted by an electronic differential liquid balance which takes account of the sloping position of the ships hull in the water.

To obtain optimum concentricity of the crankpin, the superfinishing tools 21 and 22 are applied to the crankpin with reference to the guide rollers 29 and 30 in such a way that the center 2a of the crankpin considered in cross-section is located outside a connecting line 63 between the points of contact of guide rolls 29, 30 and the cutting positions 21a and 22a of the superfinishing tools 21 and 22. The angle between the radial plane 65 and the horizontal plane 66 passing through the center of the crankpin is preferably between 35 and In such an arrangement of the superfinishing tools in relation to the guide rolls 29, 30 there is obtained a round shape with the smallest tolerance yet obtained for a crankpin.

lclaim:

1. Apparatus for grinding and superfinishing a rotary crankpin of a crankshaft while said crankshaft is being rotated along a fixed axis about its centerpin comprising a. a tool carrier,

b. at least one superfinishing tool mounted on said tool carrier for finishing the surface of said rotating crankpin,

c. support means pivotally mounted on said tool carrier,

d. a rotatably driven grinding roller mounted on said support means and having a cylindrical abrasive surface for grinding said rotating crankpin, the I10- tary axis of said grinding roller being transverse to the pivotal axis of said support means,

e. level gauge means mounted on said support means,

f. means responsive to said level gauge means for pivoting said support means to adjust and maintain the cylindrical abrasive surface of said grinding roller where it contacts the surface of the rotating crankpin in a predetermined plane,

. guide means on said tool carrier for engaging said rotating crankpin and maintaining the position of said tool carrier relative to said crankpin while said crankpin is rotating, and

h. means for moving said tool carrier towards and away from said crankshaft to cause said grinding roller and superfinishing tool] to engage and disen gage the surface of said crankpin,

i. whereby the surface of said crankpin may be both ground and superfinished precisely parallel to the axis of the centerpin of said crankshaft.

2. Apparatus according to claim 1 wherein said guide means comprises at least one guide roller for engaging said rotating crankpin.

3. Apparatus according to claim 1 further comprising a stationary support and articulate means supporting said tool carrier on said stationary support whereby said tool carrier is supported during movement of said rotating crankshaft.

4. Apparatus according to claim 1 wherein said level gauge means is mounted on said pivotal support means in a vertical plane passing through the rotary axis of said grinding roller and above the transversely extending pivotal axis of said support means.

5. Apparatus according to claim 1 wherein said means for pivoting said support means comprises a. a rod connected to said pivotal support means,

b. a stepping motor, and

c. a threaded spindle operatively connecting said motor with said rod.

6. Apparatus according to claim 4 further comprising:

means mounting said superfinisihing tool on said tool carrier for movement parallel to the rotary axis of said grinding roller and the centerpin of said crankshaft.

7. Apparatus according to claim 2 further wherein:

said superfinishing tool is mounted at a position on the opposite side of said crankpin such that the center point of the crankpin, considered in crosssection, is outside a straight line extending between the point of contact of said guide roller and the cutting position of said superfinishing tool.

8. Apparatus according to claim 7 wherein the cutting position of said superfinishing tool is in a radial plane having an angle of inclination with respect to the horizontal plane passing through the center point of the crankpin between about 35 and 10. 

1. Apparatus for grinding and superfinishing a rotary crankpin of a crankshaft while said crankshaft is being rotated along a fixed axis about its centerpin comprising a. a tool carrier, b. at least one superfinishing tool mounted on said tool carrier for finishing the surface of said rotating crankpin, c. support means pivotally mounted on said tool carrier, d. a rotatably driven grinding roller mounted on said support means and having a cylindrical abrasive surface for grinding said rotating crankpin, the rotary axis of said grinding roller being transverse to the pivotal axis of said support means, e. level gauge means mounted on said support means, f. means responsive to said level gauge means for pivoting said support means to adjust and maintain the cylindrical abrasive surface of said grinding roller where it contacts the surface of the rotating crankpin in a predetermined plane, g. guide means on said tool carrier for engaging said rotating crankpin and maintaining the position of said tool carrier relative to said crankpin while said crankpin is rotating, and h. means for moving said tool carrier towards and away from said crankshaft to cause said grinding roller and superfinishing tool to engage and disengage the surface of said crankpin, i. whereby the surface of said crankpin may be both ground and superfinished precisely parallel to the axis of the centerpin of said crankshaft.
 2. Apparatus according to claim 1 wherein said guide means comprises at least one guide roller for engaging said rotating crankpin.
 3. Apparatus according to claim 1 further comprising a stationary support and articulate means supporting said tool carrier on said stationary support whereby said tool carrier is supported during movement of said rotating crankshaft.
 4. Apparatus according to claim 1 wherein said level gauge means is mounted on said pivotal support means in a vertical plane passing through the rotary axis of said grinding roller and above the transversely extending pivotal axis of said support means.
 5. Apparatus according to claim 1 wherein said means for pivoting said support means comprises a. a rod connected to said pivotal support means, b. a stepping motor, and c. a threaded spindle operatively connecting said motor with said rod.
 6. Apparatus according to claim 4 further comprising: means mounting said superfinishing tool on said tool carrier for movement parallel to the rotary axis of said grinding roller and the centerpin of said crankshaft.
 7. Apparatus according to claim 2 further wherein: said superfinishing tool is mounted at a position on the opposite side of said crankpin such that the center point of the crankpin, considered in cross-section, is outside a straight line extending between the point of contact of said guide roller and the cutting position of said superfinishing tool.
 8. Apparatus according to claim 7 wherein The cutting position of said superfinishing tool is in a radial plane having an angle of inclination with respect to the horizontal plane passing through the center point of the crankpin between about 35* and 10* . 